Technical Field
The present disclosure relates to a light emitting device.
Description of Related Art
Light emitting devices using light emitting elements which are called light emitting diodes (hereinafter may be referred to as “LEDs”) have been attracting attention. Various types of light emitting devices that use LEDs to emit white light have known. Examples thereof include light emitting devices using combinations of LEDs to emit blue light and phosphors to emit yellow light. Such light emitting device are configured to emit white light that is a mixture of blue light emitted by blue LEDs and yellow light emitted by phosphors that emit light upon being excited by the blue light. Such light emitting devices also have good color mixing properties and thus used in a wide range of fields. Examples thereof include three-wavelength type light emitting devices in which combinations of blue LEDs, green LEDs, and red LEDs are used. Such light emitting devices are configured to emit white light that is a mixture of the lights emitted by three different colors of light emitting diodes. Such light emitting devices have the LEDs with emission spectra of sharp emission peaks and exhibit good matching with color filters of liquid crystal displays, wide color reproduction ranges, and high luminous efficiency.
In the case of light emitting devices in which light emitting elements to emit blue light and phosphors to emit yellow light are used in combination, high radiant intensity and high luminous efficiency can be obtained in visible light range, but sufficient radiant intensity in blue-green range and red range may not be obtained. For this reason, further improvement in average color rendering index that is an index of visual perception in color of an irradiated object (color rendering property) has been desired. Also, in a three-wavelength type light emitting device employing three LEDs of different colors, due to sharp emission peaks of respective LEDs, sufficient color mixing and continuous emission spectrum are difficult to obtain, and thus, higher color rendering properties may be difficult to be achieved.
Relating to the above, light emitting devices employing an LED to emit blue light and two different phosphors to emit light in a range of yellow to green range have been disclosed and referred to as devices capable of achieving high degree of color reproductivity (for example, see published Japanese translations of PCT international publications for patent applications No. 2003-535477 and No. 2003-535478).